Asymmetric-Collapse of Braced Tubes

Braced metallic tubes are used to dissipate kinetic energy in impact attenuation devices used in transportation safety applications. It is an experimentally observed fact that these braced tubes collapse asymmetrically, even under symmetrical loading conditions. This paper examines the energy dissipation characteristics of such a tube when braced across its diameter and subjected to lateral plate loading conditions. Upperand lower-bound limit analysis approaches are used to first determine the initial asymmetric collapse load of the tube with diametrical bracing oriented perpendicular to the line of action of the loads. Then, the equivalent structure technique (EST) and finite-element program, ABAQUS, are used to determine the postcollapse characteristics of the tube. Finally, these mathematical and numerical model predictions are compared with experimental results to demonstrate the accuracy of the modeling process.